At the outset, the mountainous region of Antioquia in northwestern Colombia comes across as a breathtaking natural paradise. But its picturesque valleys and winding green hills hide a chilling secret – an unusually large number of young people here suffer from a hereditary form of Alzheimer’s. Several of Antioquia’s residents are at various stages of the disease – right from early signs of memory loss to total dementia.

Early-onset Alzheimer’s is quite similar to the typical form of the disease – it is caused by toxic proteins that destroy brain cells, leading to memory loss and eventually, death. But there is one major difference – the symptoms begin to occur at a frightfully young age, sometimes even before the victim turns 40. It begins with forgetfulness and slowly progresses to disorientation and delusional ideas.

Afflicted with this form of Alzheimer’s, the people of Antioquia often reach the final stage of the disease in their mid-forties. And there’s only one explanation for the bizarre condition – it’s all in the genes. Generations of inbreeding has resulted in the spread of the defective gene in the region for the past 300 years – throughout a widely branched family that now has over 5,000 members. This makes Antioquia home to the world’s largest population of Alzheimer’s sufferers. They are all believed to have inherited the ‘paisa’ mutation, which is a simple genetic defect on Chromosome 14. The mutation is named after the people living in the area, who are known in Colombia as Paisas.

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